Battery operated, wireless monitoring of well tanks from a remote monitoring location have been used in Class 1 Division 1 locales. Tanks in the remote locations may store any type of contents such as hazardous materials such as oil or gasoline, or may store a multitude of chemicals or any other content which may be desirable to store at a remote location.
Classes and Divisions break down storage by content type. Different classes and division require different types and requirements of monitoring. For example, extremely combustible contents may require very specific and careful monitoring while more stable contents will have less strict monitoring requirements. Extremely hazardous material monitoring may require an electric monitor without any electric sparking or a securely enclosed electric system which may otherwise trigger a reaction.
In an event where a tank may have a spill or overflow, there may critical consequences to the tank storage area or local environment. Monitors are known with an alert function, but may not alert a data collection center as the spill or overflow may be imminent, before a critical situation may occur.
Classically, human monitoring has been used to monitor tanks with hazardous materials, but human monitoring may be very dangerous. A wireless monitoring system is advantageous, but batteries to power the monitoring systems will still need to be periodically replaced by a human worker. Extending battery life is important, reducing the frequency in which a battery needs to be changed. Conversely, a monitoring system may be limited by the programming to readings by specific times or intervals, where a human monitoring system may be more accurate or incident driven.
For example, Peters et al. U.S. Pat. No. 6,967,589 discloses a method of monitoring the level of tanks at a gas or oil well site with a level sensor that is coupled to a transceiver to report the level of liquid in the tanks upon request. The sensor is programmed to ‘wake up’ to report the level of liquid in the tanks when the transceiver is operational for 32 milliseconds (ms) every 4 seconds. In addition, sensor reads can take place every 100 ms for three minutes resulting in 1800 reads. The monitor ‘sleeps’ between ‘wake-ups,’ operating on little or no power, thus saving battery life. The monitoring unit can send an alarm signal to wake up the transceiver when the level of the liquid reaches a predetermined level during the 32 ms operational period.
Jenkins et al. U.S. Pat. No. 8,223,027 discloses a system for wirelessly monitoring tank levels by the use of a low-Earth orbit (LEO) satellite. The tank monitors wirelessly communicate with the satellite through a nearby satellite gateway. The monitors on the tank have a four-hour transmission interval, and are battery powered. A data collection center receives readings that can be used to provide an alarm for each individual tank. The power required to make a transmission to a satellite is significantly greater than that for a local transmission.
Bennett, Jr. et al U.S. Pat. No. 6,369,715 discloses a wireless system for monitoring tank farms wherein a transmitter with an antenna attaches to a separate level sensor by wire. The transmitter sends readings of the level sensor every 30 seconds or at a predetermined interval. The level sensor may also include an alarm switch to instruct the transmitter to broadcast an alarm signal.
The frequency of the sampling is important in order to detect any malfunction, spill, or overflow in the oil production, transmission, or storage so that any problem such as a leak or overfilling can be detected promptly and corrected quickly, or even detected before it occurs. The reality is that the malfunctions, spills, or overflows are infrequent and a high frequency sampling requires a lot of battery power. Generally, tanks and wells are in remote locations with no electrical service and battery power must be used. Furthermore, hazardous locales may require a low power monitoring system, such as battery power, where electricity may be too dangerous to run or use. There must be a balance struck between the frequency of monitoring and battery life.